1. Field of the Invention
This invention relates generally to heat engines that utilize bottoming and topping cycles and binary working fluid, and more particularly to a thermodynamic power system utilizing a binary working fluid and having a low-temperature bottoming cycle and an open or closed modified Brayton topping cycle.
2. Brief Description of the Prior Art
It is known that any thermodynamic system operating on a cycle and receiving heat while doing work must also have a heat-rejection process as part of the cycle. A statement called Carnot""s Maxim says: xe2x80x9cHeat should be added at the highest temperature and rejection at the lowest possible temperature if the greatest amount of work is to be gained and the highest thermal efficiency is to be realizedxe2x80x9d. Hot gases of combustion are produced in a combustion chamber by burning fuel in air and a maximum temperature of about 2000xc2x0 is attained. The hot gases obtained from the process are the finite heat reservoir for a thermodynamic cycle. Today""s engine design options have both theoretical and practical limits that may be described as follows. The maximum amount of heat that can be transferred from this heat reservoir would be obtained by cooling the gases from the maximum temperature to the atmospheric temperature. Note that cooling goes only to the atmospheric temperature, but not less. Theoretically, this is the xe2x80x9clowest permissible levelxe2x80x9d of temperature.
This theoretical restriction is a barrier that inhibits the development of energy technology. However, Kelvin""s statement of the Second Law of Thermodynamics does not state or imply this restriction. The development of the Second Law of Thermodynamics is based primarily on heat engine analysis. The gist of Kelvin""s statement of the Second Law Of Thermodynamics is that no cyclic process is possible whose sole result is a flow of heat from a single reservoir and the performance of equivalent work. Thus, the basic Statement of the Second Law of Thermodynamics determines only that a heat engine cannot convert into work all of the heat supplied to the working fluid; it must reject some heat.
For a hydroelectric station, the xe2x80x9clowest permissible levelxe2x80x9d of temperature is restricted by the level of the ocean. For the working process of a heat engine, the xe2x80x9clowest permissible levelxe2x80x9d of the air temperature may be significantly below the temperature of the xe2x80x9cair oceanxe2x80x9d. Furthermore, the heat engine may use the heat of that xe2x80x9cair oceanxe2x80x9d as a reservoir for producing power and cool refrigerated air simultaneously because the working fluid gas has an ability to alter its physical parameters depending on the pressure and temperature differentiate of the liquid.
Most prior art systems having thermodynamic cycles require two external heat reservoirs for the heat-addition and heat-rejection processes. however, a heat-rejection process may be made up in closed cycles without an external heat reservoir, provided that the working medium is a combined mixture of a non-condensable first gas such as helium or hydrogen and a fine dispersed low-temperature non-freezable lubricating liquid such as nitrogen, oil, water with antifreeze, etc., wherein the low-temperature liquid is used as an internal cold reservoir to carry out the heat-rejection process and the non-condensable first gas is cooled during adiabatic expansion producing useful work and serves as a coolant to heated liquid recovering from an initial condition of the gas/liquid mixture. Therefore, it is possible to construct a heat engine which will do work and exchange heat using a single external heat reservoir for the heat-addition process only. The conversion of the heat energy into another form is appreciably enhanced by employing a binary working fluid in the low-temperature closed bottoming cycle and for cooling of the working fluid of the open or closed modified Brayton topping cycles before its compression.
Heat engines are known in the art which have combined cycles such as a combination of Brayton and Rankin cycles. Fruschi, U.S. Pat. No. 5,386,685 discloses a method and apparatus for a combined cycle power plant. Simpkin, U.S. Pat. No. 5,431,016 discloses a high efficiency power generation engine. One of the principal shortcomings of these combined cycle systems is that they are not capable of cooling air before or during its compression in the topping Brayton cycle.
The present invention is distinguished over the prior art, and is a significant advance over our commonly owned previous patent application Ser. No. 09/448,557. pending and U.S. Pat. Nos. 6,161,392, and 5,996,355, which are incorporated herein by reference. A major distinction is that, in the present invention, conversion of the heat energy into another form is appreciably enhanced by employing a binary working fluid in a low-temperature closed bottoming cycle for cooling of the working fluid of the open or closed modified Brayton topping cycles during the continuous compression process. The working process of the present invention produces a cooled first gas at a cryogenic temperature in the bottoming cycle which is significantly less that the temperature of ambient air which is cooled by being drawn through a heat exchanger of the bottoming cycle and then compressed. Thus, the work of compression is significantly reduced and the amount of power is significantly increased.
The present thermodynamic power system embodiment with an open modified Brayton topping cycle using a high-temperature heat source can generate a large amount of specific power to achieve a high thermal efficiency. The present thermodynamic power system embodiment with a closed modified Brayton topping cycle can be effectively utilized as an engine for a space station using a solar heat source. Such a space energy device has significant advantages over conventional devices because it utilizes a heat-rejection process without an external heat exchanger. It also allows use of an inexpensive fuel source.
It is therefore an object of the present invention to provide a thermodynamic power system that can generate a large amount of specific power to achieve a high actual thermal efficiency.
It is another object of this invention to provide a thermodynamic power system that is inexpensive to manufacture in mass production and is inexpensive to operate, service, and repair.
Another object of this invention is to provide a thermodynamic power system that has applicability as an engine in industry, as well as applications for outer space.
Other objects of the invention will become apparent from to time throughout the specification and claims as hereinafter related.
The above noted objects of the invention are accomplished by a thermodynamic power system that utilizes a cryogenic refrigeration bottoming cycle operating on a two-phase (binary) working fluid (gas/liquid mixture) in combination with several different topping cycles. In a first embodiment the topping cycle is an open modified Brayton topping cycle using a high temperature heat source and, in a second embodiment, the topping cycle is a closed modified Brayton topping cycle. The low-temperature bottoming cycle functions to cool the working fluid of the toppings cycles.
The apparatus of the bottoming cycle includes a sliding-blade gas/liquid compressor and expander unit, a vortex separator, a heat exchanger, a plurality of liquid atomizers, a pump, gas and liquid storage tanks, temperature and pressure sensors, and control means for adjustably controlling the volume of fluids in the system contained within a thermally insulated housing. In the operation of the bottoming cycle, rotation of the gas/liquid compressor and expander rotor draws a first gas (helium or hydrogen) from the expander operating chamber into the gas/liquid compressor operating chamber.
Simultaneously, a fine dispersed low-temperature lubricating liquid (such as nitrogen, oil, water with antifreeze, etc.) is injected into the operating chamber of the gas/liquid compressor through the plurality of liquid atomizers to produce a cool gas/liquid mixture at a quantity sufficient for polytropic heat adsorption and polytropic compression of the first gas.
The compressed cool gas/liquid mixture is discharged into the vortex separator where the cool first gas that rejected polytropic heat is separated from the low-temperature liquid and supplied to the heat exchanger where it is isobarically heated using heat of ambient air as the working fluid of the open modified Brayton topping cycle or rejected heat of the working fluid of the closed modified Brayton topping cycle. The compressed and heated first gas then enters the expander operating chamber where it is adiabatic expanded and cooled doing useful work by rotating the gas expander and gas/liquid compressor rotor. The adiabatically expanded and cooled first gas with a cryogenic temperature is discharged from the gas expander operating chamber and enters the gas/liquid compressor operating chamber of the expander and compressor units and is mixed with the fine dispersed low-temperature liquid during gas compression to serve as a coolant and facilitate rejection of polytropic heat exchanging with liquid and supplement the cool gas/liquid mixture which is polytropically compressed to complete the bottoming cycle.
The apparatus of the open modified Brayton topping cycle using a high-temperature heat source with regeneration includes an air compressor, a gas turbine, a heat-exchanger/recuperator, a combustion chamber and a power apparatus. In the operation of the open topping, cycle the air compressor draws ambient air through the heat exchanger of the bottoming cycle where it is cooled. The cool air is compressed in the air compressor of the topping cycle and discharged into the heat exchanger/recuperator of the topping cycle where it is preheated using waste heat and fed to the combustion chamber. The heated air from the combustion chamber enters the gas turbine, is adiabatically expanded performing useful work and causing simultaneous rotation of the air compressor rotor. Spent working fluid from the gas turbine is supplied to the heat exchanger/recuperator isobarically giving up its waste heat to the compressed air and afterwards is exhausted.
The apparatus of the closed modified Brayton topping cycle includes a gas compressor, a gas turbine, a heat exchanger/recuperator, a heat exchanger/combustor, a gas storage tank, temperature and pressure sensors, and control means for adjustably controlling the volume at fluids in the system. In the operation of the closed topping cycle, rotation of the gas compressor rotor draws a second gas from the heat exchanger of the bottoming cycle where it is cooled. The second cool gas is compressed in the gas compressor and discharged into the topping cycle heat exchanger/recuperator where it is preheated using waste heat and then enters the heat exchanger/combustor using solar heat, geothermal heat or other heat source including an inexpensive fuel, such as coal and then enters the operating chamber of the gas turbine doing useful work by simultaneously rotating the gas turbine and gas compressor rotors. The expanded second gas from the gas turbine is supplied to the heat exchanger/recuperator isobarically giving up its waste heat to the compressed first gas. The precooling second gas is discharged from the heat exchanger/recuperator into the heat exchanger of the bottoming cycle and is cooled transferring its remainder of waste heat to the working fluid of the bottoming cycle. The expanded and cooled second gas with a cryogenic temperature is discharged from the heat exchanger of the bottoming cycle and is fed to the gas compressor and compressed to complete the closed topping cycle.